Cannot figure out error for homework beginning programmer

Question

Need a little help figuring out why the last part of my code gives an error. Can anybody tell me what's wrong? I'm working with NetBeans for an intro level programming class and cant figure out the last bit of why this is wrong.

I'm getting the following error:

Cannot find symbol symbol: variable rat04 location: class Rational

package rational;

import java.util.logging.Level;
import java.util.logging.Logger;

public class Rational {
    // the numer and denom fields represent a fraction
    // CLASS INVARIANTS:
    // CI1: denom is not 0,
    // CI2: denom is positive,
    // CI3: numer and denom are in lowest terms.
    private final int numer;
    private final int denom;

    //toString and toDouble
    public String toString() {
        return numer + "/" + denom;
    }

    public double toDouble() {
        return 1.0 * numer / denom;
    }

    //utility method
    private static int greatestCommonDivisor(int a, int b) {
        int c;
        while (b != 0) {
            c = a % b;
            a = b;
            b = c;
        }
        return Math.abs(a);
    }

    private static void testGcd() {
        System.out.println("");
        System.out.println("Test Greatest Common Denominator");
        System.out.println("");
        for (int i = -21; i < 31; i += 2) {
            for (int j = -17; j < 31; j += 3) {
                System.out.printf("\n%5d%5d%5d", i, j, greatestCommonDivisor(i, j));
            }
        }
        System.out.println("");
    }

    public Rational(int numer, int denom) throws ZeroDenomException {
        // CI1. No way to fix, must throw exception.
        if (denom == 0) {
            throw new ZeroDenomException();
        }
        // CI2. Can fix.
        if (denom < 0) {
            numer *= -1;
            denom *= -1;
        }
        // CI3. Can fix.
        int gcd = greatestCommonDivisor(numer, denom);
        if (gcd != 1) {
            numer /= gcd;
            denom /= gcd;
        }
        // all class invariants now satisfied, initialize fields:
        this.numer = numer;
        this.denom = denom;
    }

    public Rational(int book) throws ZeroDenomException {
        //this(integer, 1);
        //this(1, book);
        this(book, 1);
    }

    public Rational() throws ZeroDenomException {
        this(0);
    }

    private static void testClass() throws ZeroDenomException {
        System.out.println("Rational tests.");
        System.out.println("");

        System.out.println("Test C-tor");
        System.out.println("Expected outcome: 4/25, -4/25, -4/25," + "4/25 17/1, 0/1.");
        System.out.println("");
        Rational rat01 = new Rational(144, 900);
        Rational rat02 = new Rational(-144, 900);
        Rational rat03 = new Rational(144, -900);
        Rational rat04 = new Rational(-144, -900);
        Rational rat05 = new Rational(17);
        Rational rat06 = new Rational();
        System.out.println("rat01 = " + rat01);
        System.out.println("rat02 = " + rat02);
        System.out.println("rat03 = " + rat03);
        System.out.println("rat04 = " + rat04);
        System.out.println("rat05 = " + rat05);
        System.out.println("rat06 = " + rat06);
    }

    public static void main(String[] args) {
        System.out.println("Rational class");
        System.out.println("Implemented by (My Name)");
        try {
            testClass();
            //testGcd();  
        } catch (ZeroDenomException ex) {
            System.out.println("Zero demon exception in testClass()! (J:H)");
        }

        System.out.println("");
        System.out.println("Try bad input");
        try {
            Rational rat00 = new Rational(0, 0);
        } catch (ZeroDenomException zde) {
            System.out.println(" Expected Zero Denominator Exception. " + zde);
        } catch (Exception e) {
            System.out.println("Should not be a general Exception.");
        }
        System.out.println("");

        System.out.println("");
        System.out.println("Test toDouble. Expect 0.16");
        System.out.println("rat04 to double: " + rat04.toDouble());
    }
}

Cannot find symbol symbol: variable rat04 location: class Rational — Nick Wallace, Oct 18 '17 at 03:19
that variable is only declared in your `testClass` method, you cannot access it in `main` — UnholySheep, Oct 18 '17 at 07:07

score 2 · Answer 1 · answered Oct 18 '17 at 07:08

You declared rat04 in testClass and use it in main. The scopes are different.

You can't use a variable from one scope to another.

You can create a static variable in the class (member variable) to be accessible from both method if you want (but really should not...)

public class Rational {
    static Rational rat04;
    ...
}

Or simply don't print the value in main but in testClass where it belong.

Cannot figure out error for homework beginning programmer

1 Answers1